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I have been trying to get my old Honda running again, but I have a fuel problem. I've cleaned the carb and replaced the fuel line and filter. If I hold the carb in my hand and turn the key on the float and needle valve work perfectly. Even if I turn I'd sideways to some degree, and if I continue turning it, it will begin to overfill as it should. I straighten it up and it stops. However once bolted up it only works as long as the engine is not running. It seems the vibration is enough to cause the float and valve to be forced open, like a fuel over pressure situation. It will quickly flood the engine and even flow fuel directly into it. The fuel pump doesn't shut off and you can hear it bog down as pressure rises. Is there supposed to be a pressure regulator, or cutoff switch? I haven't measured the pressure yet but it feels like about 15 psi when we need 1 to 2 psi. I mean it really sprays! I can't seem to find anything that limits the pressure, is it supposed to be internal to the pump? Any help you can give me would be greatly appreciated. I have spent a lot of time trying to figure it out, and I really love this machine. Also I'm fighting stage 4 kidney cancer and am unable to work, and I have 6 children, so money is tight. Taking it to a shop isn't an option, and I generally enjoy working on quality equipment, but I am stumped.
 

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I had a similar problem - can't remember the name but another member on this forum pointed out that I should check the carburetor vent tube (in my case it was on a 4518 btw). If the carb vent tube is plugged up air cannot escape the float bowl as the fuel level rises and so the fuel level cannot rise far enough for the float to close the needle valve, and the pump just keeps pumping, in my case gas would actually flow out the air intake side of the carburetor (with the air filter removed). I found the vent tube to be totally stopped up with what appeared to be basic dirt, maybe caused by a bug - don't know, I replaced with a new vent tube/hose and the problem was immediately solved. Hope this helps. I was really stumped for a long time on this one til I got this tip.
 

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I had a similar problem - can't remember the name but another member on this forum pointed out that I should check the carburetor vent tube (in my case it was on a 4518 btw). If the carb vent tube is plugged up air cannot escape the float bowl as the fuel level rises and so the fuel level cannot rise far enough for the float to close the needle valve, and the pump just keeps pumping, in my case gas would actually flow out the air intake side of the carburetor (with the air filter removed). I found the vent tube to be totally stopped up with what appeared to be basic dirt, maybe caused by a bug - don't know, I replaced with a new vent tube/hose and the problem was immediately solved. Hope this helps. I was really stumped for a long time on this one til I got this tip.
just a btw note - you don't have to replace the tube with new, you can just blow it out so the carb bowl air can escape as fuel flows in, then the float "floats" and closes the fuel flow. Good Luck!
 

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Are you sure it is a OEM honda pump? It is impossible for the pump to put out too much pressure.
 

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Are you sure it is a OEM honda pump? It is impossible for the pump to put out too much pressure.
I don't know about TheRex's situation, but in mine the pump just kept pumping because the float couldn't rise enough to close the needle valve because the float bowl couldn't vent it's air out the vent tube. But, again, mine was a 4518, I think his was a 3813, maybe they work differently.
 
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